I still say you guys are underestimating Mei. She's one of the five Kage. You don't get to that level with just strength alone. You also have to be experienced, a skilled strategist and quick on your feet. A few strong techniques from Roshi won't be enough to bury Mei.
Not to mention, we have no idea what level Roshi is at
All the Jinchuriki went into Version 2, yet, they haven't gone insane:
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They're in Version 2, but they're not rampaging around like animals.
They're using their techniques and fighting tactically.
You cannot go into Version 2 and maintain your sanity unless you have control over your Bijuu like Bee does. We know for a fact that none of them had this level of control:
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The only Jinchuriki that had control of their Bijuu was Bee and Yagura (and later Naruto). This means that Tobi's control over them has
something to do with it.
Not to mention that Han even transformed into the Gobi:
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Which he cannot do on his own because he didn't have control of his Bijuu
Without Tobi's Six Path chakra receiver influence we don't even know if Roshi can utilize Version 2 like he has thus far.